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Control of Movement and Posture
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
There are three basic balance control strategies that are induced by perturbations (Figure 13.6). The first is the ankle strategy, which involves sequential activation of the ankle, thigh, and hip muscles, progressing distally to proximally on the same dorsal or ventral aspect of the body, depending on the direction of the perturbation and with a delay of 70–130 ms. For example, if the support surface on which a person is standing is moved so as to induce a forward sway (Figure 13.6a), this would result in the activation of the ankle plantar-flexors (gastrocnemius, soleus, and plantaris), the knee flexor (biceps femoris) and the hip extensors (mainly the gluteus maximus and the hamstring muscles). Balance is restored through rotation of the body about the ankle joints, which can rotate in all directions. The ankle strategy is limited by the torque that can be exerted by the foot in contact with the supporting surface and would be used for slow and small perturbations and when standing on uneven terrain.
Terrestrial Locomotion
Published in Malcolm S. Gordon, Reinhard Blickhan, John O. Dabiri, John J. Videler, Animal Locomotion, 2017
Such a pantograph muscle can generate tension under different joint angles without changing length, that is, contraction velocity is decreased. The biarticular M. gastrocnemius may be able to extend the ankle in phases in which the mono-articular muscle (e.g., M. plantaris) is running out of power as long as the moment of the knee flexors is sufficient to overcome the opposing moment of the M. gastrocnemius at the knee. In such a situation, indeed a part of the power of the knee extensors that is lost at the knee due to the antagonistic operation of the M. gastrocnemius is not lost or absorbed by M. gastrocnemius lengthening, but instead is transferred to the ankle joint. That means the extending knee supports extension at the ankle joint. van Schenau (1989) pointed out that this coupling can be used to control force direction. Joints generate force components at the leg tip tangential to the leg axis. To generate an axial force in a trisegmented leg, it is necessary to generate a counteracting moment at the second joint. The coactivated muscle helps to do this.
Neurophysiology of Joints
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
Håkan Johansson, Per Sjölander
In 1979, Appelberg et al. (128,129) demonstrated that natural stimulation of joint receptors could excite primary spindle afferents via the γ-spindle loop. Johansson et al. (126) later demonstrated that receptors in the ipsi- and contralateral knee, ankle, and hip joints, activated by pressure on the capsule, could potentially influence dynamic and static fusimotor neurons projecting to the ipsilateral gastrocnemius-soleus-plantaris muscles. They observed that the effects on the ipsilateral γ-muscle-spindle system elicited by contralateral knee or ankle extension-flexion to a considerable extent were induced from joint afferents (Fig. 8).
Aponeurosis behaviour during muscular contraction: A narrative review
Published in European Journal of Sport Science, 2018
Other factors, which likely interact with muscle length and its contractile state, might also influence aponeurosis behaviour and its subsequent longitudinal stiffness. Muscles with one or more compartments that exhibit relatively homogeneous (van Donkelaar et al., 1999; Zuurbier et al., 1994) or heterogeneous architectures (Böl et al., 2015; Finni, Hodgson, Lai, Edgerton, & Sinha, 2003; Maganaris & Paul, 2000) will likely affect aponeurosis behaviour by applying spatially variable forces onto it (Englund, Elder, Xu, Ding, & Damon, 2011). For example, Böl et al. (2015) showed that the three-dimensional aponeurosis strain distributions in active and passive muscle are both irregular, with a V-shaped strain distribution reported in the proximal aponeurosis of the rabbit plantaris under muscle activation, compared with a distally centred strain distribution during passive stretch. Strain distribution differences might also be present within the aponeurosis due to submaximal activation of specific motor units within a muscle compartment (Akima, Ito, Yoshikawa, & Fukunaga, 2000; Finni et al., 2003), which may cause shear within the aponeurosis (Englund et al., 2011; Finni et al., 2003). Similarly, localised activation of distal muscle fibres would reduce the effective aponeurosis length and result in a completely different aponeurosis strain distribution compared with a globally distributed activation of muscle fibres. Therefore, architectural heterogeneity and muscle activation differences across motor tasks and contraction types likely complicate aponeurosis behaviour even at the same muscle length and force.
Does radiofrequency application improve function and reduce pain in patients with insertional Achilles tendinopathy? A retrospective study with a minimum 2-year follow-up
Published in Research in Sports Medicine, 2023
Yujie Song, Xiao’ao Xue, Yinghui Hua
Achilles tendinopathy causes persistent tendon pain, which leads to compromised function and participation in work and recreation activities (Scott et al., 2020). It has been reported to affect 9% of recreational runners and up to 5% of professional athletes end their careers due to the debilitating effects of this condition (Lysholm & Wiklander, 1987). It could be furtherly subdivided into insertional and midportion tendinopathy based on their distinct aetiology, injury mechanism, and affected location (Li et al., 2017). Insertional Achilles tendinopathy (IAT) may also present with retrocalcaneal bursitis, Haglund’s deformity and calcific deposits within the substance of the Achilles tendon proximal to its calcaneal insertion (Touzell, 2020). Currently, non-surgical treatment is usually the first choice for Achilles tendinopathy, but no univocal evidence exists regarding the best management (Aicale et al., 2020; de Vos et al., 2021). Various non-operative treatment options are available for IAT, including heel lifts (Wilson et al., 2018), eccentric or stretching exercises (Murphy et al., 2019; Porter et al., 2002), shockwave therapy (Liao et al., 2018), and injection therapy (Boesen et al., 2019; Madhi et al., 2020). For cases refractory to non-operative treatment, surgery can be beneficial. This involves an open or arthroscopic debridement of the Achilles tendon, plantaris resections, excision of the Haglund’s deformity and removal of the inflamed retrocalcaneal bursa (Masci et al., 2021; Touzell, 2020). However, surgical procedures might not always be effective as the poor relationships between changes in structure and changes in patients’ symptoms (de Vos et al., 2012).
Self-reported foot strike patterns and sonographic evidence of Achilles tendinopathy in asymptomatic marathon runners
Published in Journal of Sports Sciences, 2022
Scott M. Marberry, Sara E. Filmalter, George G.A. Pujalte, James C. Presley, Kristina F. DeMatas, Daniel P. Montero, Krishna Israni, Colleen T. Ball, Jennifer R. Maynard
Significant findings in this study included larger median CSA in men versus women and in runners with high BMI. The average CSA for men was 70 to 72 mm2 versus 56 to 57 mm2 for women. BMI analysis discovered a 1 mm2 increase in CSA for every 1 kg/m2 increase in body mass. These subtle differences should be considered when using ultrasound to view the Achilles tendon. Aside from BMI, investigation of the participant’s lower extremity anatomy, bilateral calf strengths, and gait analysis may also play a variable role in the tendon thickness. The nature of the participants’ training regimen,(Hansen et al., 2003; Milgrom et al., 2014) limb dominance,(Chiu et al., 2016; Ying et al., 2003) and running mechanics (Kernozek et al., 2018; Lyght et al., 2016) could also potentially affect loading through the Achilles tendon and thus affect modelling, although results in previous studies have been mixed. Triceps surae or plantaris tendon type could also affect the CSA. Studies have shown relationships in the architectures of these muscles,(Geremia et al., 2018; Spang et al., 2016; Zellers et al., 2019) which may be affected by heel-striking or forefoot-striking, with changes that may be apparent through sonography. The gastrocnemius and soleus muscles differ in muscle fibre type (Moritani et al., 1991) and as such, have been noted to differ in function (Bryan Dixon, 2009; Cronin et al., 2013). Their differences in activation patterns and function may cause the subtendons of the Achilles tendon to be overloaded differently depending on mechanics and training, the morphological effects of which deserve more investigation via sonography. It would be interesting to see if there are changes to the subtendons and how they correlate with noted changes to the Achilles tendon. Future studies should look at the above variables, perhaps incorporating a torque velocity device to determine objective force data (Trappe et al., 2001).